Electrolytic condenser



F. EVERS ET AL 09,770

ELECTROLYTIC CONDENSER July 30, 1940.

Filed July 5, 1936 ,EFi-ilz Gvers Wernr Bierrrnann -Paul urernen IN VENT0R5 ATTORNEY.

Patented July 30, 1940 UNITED STATES PATENT. OFFICE mann,

Berlin Charlottenburg,

and Paul Werner, Berlin-Neulichtenberg, Germany, assignors, by mesneassignments, to Radio Patents Corporation, a corporation of New YorkApplication July s, 1936, Serial No. 88,700 In Germany July 12, 1935 6Claims. (Cl. 175-315) Our invention relates to electrolytic devices,such as condensers, and to a method of making such condensers.

Electrolytic devices, such as condensers, are provided with electrodescontacting an electrolyte. At least one electrode is provided with adielectric film formed on it. A spacer containing or permeated by theelectrolyte is arranged between the electrodes.

It is an object of the invention to improve' the manufacture ofcondensers ,of this type'and to render it more compact.

Another object is to secure a complete and homogeneous impregnation ofthis separator.

Another object of the invention is to provide an electrolytic condenserhaving a unitary fibreless spacer and electrolyte.

A further object is to provide a unitary electrode and separatorcomprising a non-fibrous spacer adhering to the electrode.

Aspecific object is to provide a unitary electrode and spacer elementready for assembly in a condenser vstructure.

These and further objects of the invention will become more apparent.from the following description with reference to the accompanyingdrawing in which Fig. 1 illustrates diagrammatically an electrolyticcondenser of the rolled type with the ends of the electrode and spacerstrips partly unrolled, while Fig. 2 is a cross-section on an enlargedscale of a unitary electrode and conductive spacer according to theinvention.

In the construction of electrolytic condensers, it has been customary touse a fibrous material such as cotton or paper as a spacer separatingthe electrodes. Such separators require considerable space. It has alsobeen proposed to use a fibreless spacer of cellulose derivative knownunder the trade-name Cellophane. 'When using a material of thischaracter as a spacer in electrolytic condensers, care must be takenthat the electrolyte completely impregnates the Cellophane. Themanufacture of porous Cellophane isv quite difficult. The Cellophanecontains also side products incidentally produced in the manufacture ofthe Cellophane. Thus, the Cellophane usually contains sulphurettedhydrogen or sulphates or other reducing substances. These and other sideproducts contained in the Cellophane are liable to impair the properfunctioning of the condenser.

The above mentioned and other disadvantages are substantially overcomeby the invention which uses preshaped gelatin, preferably'in the form ofsheets or strips as a spacer and carrier. of the electrolyte inelectrolytic condensers.

The gelatine as a spacer material may be provided in different forms,some of which will be described hereafter. In accordance with one 5method, gelatine sheets or foils are used produced by casting gelatinupon a glass or metal base. Such processes are well known in the art anddescribed for instance in a publication by Dr. M. Halama,Chemisch-technischer Verlag Dr. Boden- 10 backer, entitled'Iransparentfolien. The gelatine foils or plates are then soaked in theelectrolyte which causes the foils to swell and become thoroughlyimpregnated with the electrolyte.

The gelatine can be mixed, however, with the electrolyte and the mixturethen cast into foils, strips or plates. Thereby a unitary or compositegelatin-electrolyte sheet is obtained. This gelatin-electrolyte sheet ofproper size can be used as such in the assembly of a condenser, or woundinto a roll for storage and used later on when desired. If the sheet hasbeen dried, any suitable liquid solvent in proper amount can be addedbefore assembly of the condenser.

The gelatin-electrolytic composition, or liquid or plastic mixturethereof, can also be applied to the metallic elements, or electrodes, ofthe condenser in such a way as to obtain a unitary electrode .andconductive spacer element. To this end, a coating of agelatin-electrolyte composition is applied to the electrode such as ametal strip, by casting or similar process. The electrode may be eithera plain metal electrode or formed i. e. covered on one or two sides witha dielectric film.

The following is an example for producing a suitable mixture of agelatin-electrolyte for use according to the invention.

Electrolytes for use in electrolytic condensers should have a properpI-Ivalue or degree of ion concentration which remains substantiallyconstant, and the value of whichamounts in general to about 4-6, i, e.is coming within the range of weak acids. A suitable acid constituentsuch as boric acid or a mixture of boric acid and a borate,

is preferably admixed to the gelatin before ad- 5 mixing the electrolyteor other constituents of it. Moreover, so-called bufier materials may beadded such as acetates or mixtures of acetic acid and alkali acetates,citrates or mixtures of citrates and alkali citrates. The latter havethe effect of preventing substantial variations of the pH value of theelectrolyte.

In order to render the condenser suited for operating temperature abovethe softening tem- 5 dill perature of gelatin, the gelatin may besubjected to well known hardening processes.

It has furthermore been found advantageous to add substances to thegelatin rendering the foils sufllciently flexible and pliable. There maybe added ingredients increasing or decreasing the hydroscopity of thefoil. To this end, a suitable oil, such as castor oil, beeswax, carnaubawax, Vaseline, formaline, boric acid, may be added to the gelatine.Adding such as boric acid and formaline have the further effect ofcounteracting possible decomposition of the gelatine which is an organicsubstance caused by bacteria.

It was found that condensers made in accordance with the improvementsand method described require less space and possess high breakdownvoltage compared with condensers made according to heretofore knownmethods.

Referring to the drawing, we have illustrated therein diagrammaticallyan electrolytic condenser of the rolled type suitable for practicing theinvention. Referring to Fig. 1, the condenser shown comprises a pair of'compositegelatine and electrolyte strips l and 2 serving as separatorsinterleaved with a pair of metal foils 3 and 3, and wound into a roll.At least one of the foils has a dielectric film formed thereon, suchasby an electrochemical process well known in the art. The dielectric filmcan beformed prior to the assembly of the metal foils with the spacerelements into the condenser body or roll, or the film may be formed, oraged, after completion of the condenser assemblage by applying aforming, or aging potential to the electrodes in a known manner.

The forming of the electrodes can be carried out according; to anyprocess known in the art, and the electrodes may be subjected topreparatory treatment such as an etching operation either chemical ormechanical to improve the electrical characteristics of the condenser ina known manner.

Figure 2 is an enlarged cross-section of a felt 5 coated with a gelatinspacer 6 such as described above. A unitary structure of this type is ofparticular advantage if used for foils having minute surface eievationsand depressions, such as an etchedlioil, or foilhaving a roughenedsurface. in these cases the spacer soaked in electrolyte is applied,enters into all craters or depressions, thus preyenting voids betweenthe electrode surface and the electrolyte, and insuring good physicalcontact between them. Thereby desirable improvements of thecharacteristic of the condenserfincluding a substantial reduction of itsinternal resistance and increase of its capacity are obtained.

It is evident from the above that many changes may be made in themanufacture and structure of I the condenser described and materialsused, coming within the broadest scope and spirit of the invention asdefined in the appended claims.

What we claim is:

1.111 a method of manufacturing an electrolytic device, such as acondenser, composed of metal-foil electrodes separated by a sheet-likespacer containing an absorbed electrolyte, the steps of applying plasticor liquid .gelatine to at least one side of a metal-foil electrode toform a thin layer thereon substantially covering said electrode side,solidifying said layer on said elec= trode so as to form acoherent unittherewith,

soaking said-layer of the unit with an electrolyte, and assembling anumber, one as aminimum, of said units into an electrolytic body. 2. Ina method of manufacturing an electrolytic device, such as a condenser,composed of metal-foil electrodes separated by a sheet-like 5 spacercontaining an absorbed electrolyte, the

steps of applying plastic or liquid gelatine to at least one side of ametal-foil electrode to form a thin layer thereon substantially coveringsaid electrode side, solidifying said layer on said electrode so as toform a coherent unit therewith,

soaking said layer of the unit with an electrolyte,

interleaving a number, two as a minimum, of said units and rolling theminto an electrolytic body. I

3. In a method of manufacturing an electrolytic device, such as acondenser, composed of metal-foil electrodes separated by a sheet-likespacer containing an absorbed electrolyte, the steps of applying plasticor liquid gelatine to at least one side of a metal-foil electrode toform a thin layer thereon substantially covering said electrode side,solidifying said layer on said electrode so as to form a coherent unittherewith, soaking said layer of the unit with an electrolyte, treatingsaid layer united with said electrode so as to render it indifferent tochanges of temperature, and assembling a number, one as a minimum, ofsaid units into an electrolytic body.

4. In a method of manufacturing an electro lytic device, such as acondenser, composed of metal-foil electrodes separated by a sheet-likespacer containing an absorbed electrolyte, the steps of applying plasticor liquid gelatine containing a softening medium to at least one side ofsaid electrode to form a thin layer thereon substantially covering saidelectrode side, solidiiying said layer on said electrode so as to form acoherent unit therewith, soaking said layer of the unit with anelectrolyte, and assembling a number, one as a minimum, of said unitsinto an electrolytic body.

5. In a method of manufacturing an electrolytic device, such as acondenser, composed of metal-foil electrodes separated by a sheet-likespacer containing an absorbed electrolyte, the steps of applying to atleast one side of said electrode a mixture of liquid or plastic gelatineand means capable of affecting the hygrosccp y of said mixture selectedfrom a group consisting of oil, castor oil, bees-wax, carnauba wax andVase line, its form a layer thereon subst itially covering saidelectrode side,'solidiiying said layer on said electrode as to form acoherent unit therewith, soaking said layer of theunit with anmetal-foil electrodes separated by a sheet-like spacer containing anabsorbed electrolyte, the steps of applying a liquid or plastic mixtureof gelatine and some constituents of an electrolyte to at least one sideof a metal-foil electrode to electrode so as to form a coherent unittherewith,

soaking said layer of the unit with a liquid mainder of the electrolyte,and. assembling a number, one as a minimum, of said units into is anelectrolytic body.

FR"TZ EVERS.

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